1.

program chia_het;

uses crt;

var n: real;

begin

clrscr;

writeln('nhap so n:'); readln(n);

if (n mod 3)=0 then writeln(' chia het cho 3:')

else writeln(' ko chia het:');

readln;

end.

2.

program tong_chan;

uses crt;

var N,dem:integer;

Tong:longint;

BEGIN

Clrscr;

writeln('Nhap so nguyen N =');

readln(N);

Tong := 0;

dem := 0;

while dem < N do

begin

Tong := Tong + dem*2;

dem := dem + 1;

end;

write('Tong', N, 'so tu nhien chan dau tien la: ',Tong); 

readln;

END.

3.

program chungminh;

uses rt;

var sbc,sc,thuong:integer;

begin

clrscr;

write('Nhap so bi chia: ');   readln(sbc);

write('Nhap so chia: ');  readln(sc);

thuong:=0;

while sbc>=sc do

 begin

  inc(thuong);

  sbc:=sbc-sc;

 end;

writeln('Thuong la: ',thuong);

writeln('So du la: ',sbc); 

{so du la sbc, sau khi tru xong thi sbc luon be hon sc va do la phan con lai khong chia het}

readln

end.